How to automate a Game application?

I tried to automate a Unity3d game(android apk) with testdroid tool. Whats the problem is, the tool is unable to identify the element in the game, instead performing "clickOnScreen()" blindly clicking on the screen

solo.clickOnScreen(solo.toScreenX(0.665f), solo.toScreenY(0.452f));

I am unable to get the required results with this sort of automation.

What is the best tool used for game automation? How it works?

Anyone tell me how to automate in testdroid in a better way or suggest me other tool which could detect the game element or any other procedure that works well for game automation.

Thanks